blitzkit/packages/website/src/core/i18n/getBestLocale.ts

import locales from "@blitzkit/i18n/locales.json";

export function getBestLocale() {
  const desiredLocale =
    localStorage.getItem("preferred-locale") ??
    navigator.language.split("-")[0];
  const isSupported = locales.supported.some(
    ({ locale }) => locale === desiredLocale
  );
  const isDefault = desiredLocale === locales.default;

  if (!isSupported || isDefault) return undefined;

  return desiredLocale;
}